Quick time-frequency synchronizing method under low signal-to-noise ratio

Abstract

The invention discloses a quick time-frequency synchronizing method under the low signal-to-noise ratio. The method is used for time-frequency synchronization of signals between a transmitting terminal and a receiving terminal. The method specifically comprises the following steps that (1), a linear frequency modulation sequence is used as a spread spectrum sequence of a data package, wherein the cycle is N, and the cycle width is Tc; (2), the linear frequency modulation sequence of one cycle serves as a local sequence, moving correlation is carried out on the spread spectrum sequence of one cycle and the received local sequence from the beginning of time t, a first correlation peak value is obtained, and the position where the first correlation peak value occurs is tp; (3), moving correlation is carried out on the spread spectrum sequence of another cycle and the local sequence from the beginning of time (t+delta T), and a second correlation peak value is obtained; (4), the phase difference delta theta between the first correlation peak value and the second correlation peak value is solved, a frequency offset estimation value fd=delta theta / 2*pi*delta T is obtained to carry out frequency offset compensation on the data package, and the frequency synchronization is finished; (5), the correlation peak value position offset nd=round(fdNTc) is calculated, the initial position of the spread spectrum sequence is tp+ndTc, and time synchronization is finished, wherein the correlation peak value position offset is caused by frequency offset.

Description

technical field [0001] The invention relates to a method for rapidly completing time and frequency synchronization in a low signal-to-noise ratio environment, and belongs to the technical field of wireless communication. Background technique [0002] In the modern wireless communication system based on spread spectrum, the transmitter and the receiver are usually used for data transmission, the spread spectrum sequence is sent by the transmitter, and the boundary of the spread spectrum sequence is found and received by the receiver. Due to the instability of the oscillators in the transmitter and receiver, there is generally a certain value of frequency offset in the transceiver, and when the transceiver is in high-speed motion, it will also be affected by Doppler frequency shift. [0003] The transmitter and receiver are therefore time-synchronized and frequency-synchronized before data transmission begins. The purpose of time synchronization is to find the boundary of the...

AI Technical Summary

Problems solved by technology

[0008] In view of this, the present invention provides a fast time-frequency synchronization method under low signal-to-noise ratio, which solves the problem of low efficiency and large amount of calculation for time-frequency synchronization using traditional algorithms problems, shorten the time required for time-frequency synchronization, and reduce the computational complexity

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